In one aspect, this invention relates to hydrophilic polypropylene fibers which preferably have antimicrobial activity. In another aspect it relates to a multilayer absorbent device suitable as, e.g., a wound dressing,a medical drape, and the like.
Briefly, in one aspect, the invention provides a polypropylene fiber having incorporated therein a C8 to C16 fatty acid monoglyceride or a mixture of glycerides containing at least 80 percent by weight of one or more C8 to C16 fatty monoglycerides, and a hydrophilic enhancer material. The invention includes fibrous nonwoven, woven and knit webs and batts made from such fibers.
In another aspect, the invention provides a hydrophilic polypropylene fiber comprising: (a) polypropylene; (b) an effective amount of at least one C8 to C 12 fatty acid monoglyceride added to the polypropylene as a melt additive to impart both hydrophilicity and antimicrobial activity to Gram-positive bacteria to the surface of the fiber; and (c) an effective amount of an antimicrobial enhancer material such that the surface of the fiber is antimicrobial to Gram-negative bacteria such as Klebsiella pneumoniae. Preferred antimicrobial enhancer materials include organic acids and chelating agents, most preferably lactic acid.
In another aspect, the invention provides an absorbent device comprising: (a) an absorbent layer having upper and lower opposed, major surfaces and comprising fibers that are hydrophilic and, preferably, antimicrobial to Gram-positive bacteria; and (b) a liquid-impermeable and moisture vapor permeable backing sheet adhered to the upper surface of the absorbent layer. The fibers comprise polypropylene and an effective amount of at least one C8 to C16 fatty acid monoglyceride added to the polypropylene as a melt additive to render the surface of the fibers hydrophilic and, preferably, antimicrobial. In one preferred embodiment of this invention, the surface of the hydrophilic fibers are treated with an effective amount of an antimicrobial enhancer material, such as lactic acid, such that the surface of the fibers in the absorbent layer are antimicrobial to Gram-negative bacteria.
In one embodiment of the absorbent device, the absorbent layer and backing sheet are substantially coextensive. When the absorbent device is used as a wound dressing, it can be positioned over the wound with the absorbent layer positioned adjacent to the wound. The device is then adhered to the skin around the wound, for example, by tape. In another embodiment of the absorbent device, the absorbent layer and the backing sheet are not substantially coextensive and the backing sheet extends beyond at least a portion of the outer perimeter of the absorbent layer to form an extended portion with an upper and lower surface. The lower surface of the extended portion is adjacent to the absorbent layer and at least a portion of the lower surface carries an adhesive layer which can be used to adhere the absorbent device to the skin around the wound. Optionally, this embodiment can further comprise a release liner that is substantially coextensive with the backing sheet and adhered to the backing sheet by the adhesive layer. The release liner would be removed from the absorbent device prior to application to a wound.
A preferred embodiment of the absorbent device further comprises a liquid-permeable sheet that is substantially coextensive with, and adhered to, the lower surface of the absorbent layer. The liquid permeable sheet permits passage of liquid, e.g., exudate, from the wound into the absorbent layer, and preferably prevents adherence of the absorbent layer to the wound. Optionally, the liquid permeable sheet can be hydrophilic or antimicrobial, or both.
The invention also provides useful devices made from such fibers, such as fabrics, webs, batts, and single and multi-layer nonwoven constructions, which are employed in the manufacture of wound dressings, medical drapes, surgical gowns, surgical masks, disposable diapers, filter media, face masks, orthopedic cast padding/stockinettes, respirators, food packaging, dental floss, industrial wipes, textiles, and battery separators. In particular, the absorbent device of the present invention can advantageously be used as a wound dressing because it can (i) absorb a substantial quantity of wound exudate when the dressing is worn for an extended period of time or when the wound produces a large quantity of exudate, and (ii) retard growth of bacteria in the absorbent layer, and, in some cases, in the wound. A further advantage of the absorbent device is that the antimicrobial activity of the device reduces the sterilization load associated with the wound dressing when the device is sterilized prior to packaging such as, for example, by exposure to ethylene oxide.
The invention further provides a method of preparing fibers that are both hydrophilic and, preferably, antimicrobial to Gram-positive and Gram-negative bacteria, the method comprising the steps of (i) preparing a hot melt mixture comprising melted polypropylene and an amount of at least one C8 to C16 fatty acid monoglyceride that is effective to impart both hydrophilicity and, preferably, antimicrobial activity to Gram-positive bacteria to the surface of the fiber; and (ii) shaping the mixture into the desired shape, for example forming the fibers by extrusion through a die. When it is desired that the fibers also be antimicrobial to Gram-negative bacteria, the method further comprises the step of contacting the shaped mixture with a liquid composition comprising at least one antimicrobial enhancer material, thereby cooling and at least partially solidifying the shaped mixture and, when present, evaporating sufficient solvent or carrier liquid from the liquid composition to yield an essentially dry coating of the antimicrobial enhancer material on the surface of the shaped mixture that is of sufficient concentration and uniformity such that the extruded surface is antimicrobial to Gram-negative bacteria. When both hydrophilicity and antimicrobial activity are desired, preferably the monoglyceride is a C8-C12 fatty acid monoglyceride, such as, for example, glycerol monolaurate. Some embodiments of the aforementioned fibers further incorporate an effective amount of a hydrophilic enhancer material added to the polypropylene as a melt additive to enhance the hydrophilicity of the fibers.